The rotating drum for workpiece conveyance of this type (hereinafter refer to simply as “rotating drum” in some cases) is used in a workpiece conveyance device for conveying a variety of workpieces such as metal machined articles, plastic molded articles, ceramics and other inorganic machined articles, rubber articles, earth and sand, and food products.
Patent documents 1 to 4 each disclose a workpiece washing device for washing workpieces in a rotating drum by spraying washing liquid to the workpieces being fed by a feed fin rotating integrally with the rotating drum. The feed fin extending helically along the inner circumferential surface of the rotating drum, is generally a plate-like fin which has a constant width and a constant height, and erects at a right angle from the inner circumferential surface of the rotating drum. Patent document 5 discloses a rotating drum for washing provided with a feed fin slightly inclined in the feed direction.
Workpieces, which are conveyed within the rotating drum, are positioned on the inner circumferential surface section located at the lowest part of the drum inner circumferential surface. When the rotating drum rotates once, the workpieces are caused to feed out in the direction of the drum center line by one pitch of the feed fin rotating integrally with the rotating drum.
The present inventors et al have proposed a rotating drum for use in a workpiece cleaning device, in which liquid passable portion and liquid impassable portion are formed along the circumferential direction in Patent document 6. In the workpiece cleaning device disclosed in this document, a workpiece inserted into the rotating drum is conveyed by the feed fin while the washing liquid is sprayed onto the workpiece. While the rotating drum rotates once, the workpiece is applied with three manners of washing; immersion washing, washing by running liquid, and shower washing. Hereinafter, this type of washing is called as a “triple washing.”
In the triple washing, when the liquid impassable section moves to a lower side of the rotating drum, washing liquid is accumulated on the liquid impassable section and the workpiece becomes a state being immersed in the washing liquid, whereby the workpiece is primarily applied with immersion washing. In a state in which the lower side part of drum is gradually switched from the liquid impassable section to the liquid passable section with the rotation of the rotating drum, the washing liquid accumulated on the liquid impassable section flows out through the liquid passable section, and therefore the workpiece is primarily applied with washing by running liquid. In a state in which the liquid passable section is located at the lower side part of the drum, washing liquid is directly sprayed onto the workpiece, and shower washing is primarily performed on the workpiece.